This invention relates generally to safety devices for vehicles that travel on a rail. Specifically, the invention relates to double end or bi-directional derails for derailing and thereby stopping a runaway railed vehicle traveling in either of two directions on a rail system.
Derails are devices that are situated on or near a rail and which may be selectively positioned with respect to the rail so as to cause a runaway railcar to become derailed. Derails are useful, for example, to protect personnel or other rail vehicles from harm. As exemplified by U.S. Pat. No. 2,829,246, the subject matter of which is hereby incorporated by reference in its entirety, bi-directional slidable derails are known. These devices typically comprise a derail shoe having derailing bars, and a guide box to allow the derail to be moved into and out of the derailing position.
Such prior art derail configurations are typically damaged after use, necessitating replacement or considerable repair of the derail. Usually, significant deformation and damage to the derail shoe occurs as a result of the impact of the rail vehicle wheel with the derail shoe. This is due to the high thrust load of the railed vehicle wheel against the derail shoe during impact. As a result of the high thrust load in prior art derails and the massive construction required to withstand the large impact forces of very heavy railed vehicles, prior art derails are characterized by significant weight and material cost. On the other hand, excessive weight is undesirable since a great deal of manual or automated effort is required to install and actuate derails in general. Thus, derail construction efforts have focused on providing for sufficient diversion or absorption of the thrust load while maintaining reasonable or practical weight of the derail assembly.
U.S. Pat. No. 2,829,246, describes the use of slight deflection angles on single directional derails. However, such modifications to single directional derails have heretofore been recognized as disadvantageous when applied to bi-directional derails because the resulting configuration is often too heavy. In fact, the prior art exemplified by U.S. Pat. No. 2,829,246 discloses only compact bi-directional configurations which have rather abrupt deflection angles and Thus, prior art bi-directional derails suffer from the disadvantage of sacrificing more gradual deflection angles in favor of providing a compact design. It would therefore be desirable to provide a bi-directional derail construction which reduces the thrust load of the railed vehicle during impact by providing gradual deflection angles while maintaining the overall derail weight and material cost within practical limits.